In general, snow removal agents are classified into snow melting (ice melting) agents, which melt snow directly, and abrasive agents, which do not melt snow but temporarily increase friction on the snow-covered or frozen road surface.
Typically, sand is used as abrasive agent. Although it temporarily increases friction, a consistent effect cannot be expected as the sand particles gradually settle down and are buried in the snow. Further, they cause the clogging of drainage pipes and water collection tanks, air pollution, damage to vehicles, etc., requiring more workforce and further cost. Thus, sand is restrictively used in ascending slopes, shaded areas, constantly frozen areas, bridges with no heat supply from the ground, etc.
The snow melting agents are largely classified into chlorides and non-chlorides. Chlorides are preferred to non-chlorides because of superior snow removal effect.
Of the chloride snow removal agent, calcium chloride is typically used because, when sprayed on snow or ice, it melts the snow or ice with strong water absorbency and exothermicity.
The heat required to melt the snow or ice (80 cal/1 g of ice) is provided by the heat of dissolution of calcium chloride (175 cal/g).
However, calcium chloride corrodes vehicles or metallic fixtures because of strong corrosiveness and, when absorbed in the soil, it causes yellowing or withering of plants.
In addition, calcium chloride causes the cracking of road surface because of the high heat of dissolution and is inconvenient to store because of high hygroscopy. In particular, it tends to become hardened when stored for a long time.
Further, when flown into rivers, calcium chloride causes the death of fish and shellfish.
And, in the case of the outer roads or bridges with light traffic, calcium chloride sprayed on the road surface tends to get wet and freeze again, requiring re-spraying of calcium chloride or resulting in freezing and clogging of drains.